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Exchange 2010 HA Questions

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Exchange 2010 HA Questions - 6.Nov.2009 10:13:00 AM   
a_user

 

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Its my understanding that for 100% redundancy of an exchange 2010 environment you need a redundant cas array on independent servers, a redundant HT array on separate servers and  your mailbox servers on separate servers. So in other words 6 separate servers not counting edge and unified messaging (if that is part of your environment).

My question is, is it possible to combine the cas and hub servers in a cluster to eliminate 2 servers while still retaining 100% HA? What about combining the cas, HT and mailbox roles (with the dag’s)? Is that possible? If doing so are you able to provide 100% availability to the cas and HT roles in this configuration? Im thinking not due to a shared hostname.

We want to provide the most high availability possible but are also concerned about the amount of hardware and of course licenses required. Looking for some suggestions.

Thanks
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RE: Exchange 2010 HA Questions - 6.Nov.2009 10:20:08 AM   
mark@mvps.org

 

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In 2010 you can now put the CAS and HT on the MBX role and still have HA. Whether I would or not is open to debate. I think I would virtualize all of the roles down to two bits of tin and spread the guests around appropriately.

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Mark Arnold (Exchange MVP)
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RE: Exchange 2010 HA Questions - 6.Nov.2009 11:13:41 AM   
a_user

 

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Thanks Mark. Im glad to hear this a possibility. My concern with running each of these services on seperate servers, whether virtual or physical, imo is the added complexity. I understand that seperation of the roles can improve stability and availability but it also adds additional servers to the environment where there are increased points of failure. Not as much of an issue if you have redundant servers for each role, but the way I see it, if something stops working, you now have a number of servers to try and narrow down where the problem exists as opposed to one or two.

I am curious of your stance on combining the roles though if the hardware was more then suitable to handle the load. The impression I get is you would be against it if you had the choice. Why is that?

Perhaps some background. We have about 600 mail enabled users, one cas server, one edge, one HT/MBX. We want to introduce HA to our local environment as well as a remote data center (where we intend to run all roles minus the edge). I was hoping to implement a single edge, a dual cas and dual ht/mbx server.

(in reply to mark@mvps.org)
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RE: Exchange 2010 HA Questions - 6.Nov.2009 11:22:43 AM   
mark@mvps.org

 

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It might sound counter intuitive but separating the roles is actualy simpler. Combine the roles and you intermesh things. Keep them separate and your interactions between the services is simplified down to the offending protocols.

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RE: Exchange 2010 HA Questions - 9.Nov.2009 3:52:32 AM   
ismail.mohammed

 

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hi mate,

I agree with Mark as well.
If I need to go with HA on Exchange 2010, two concerns will be running in my mind..
Do i need to have HA for all server roles or just i need to have HA for MBX.

If i am concerned for just MBX and few number of users then DAG where i can rest of the server roles HT, CAS.

If i am concerneed about the n numbers of mbx and HA for all server roles then i need to go with single MBX server HA and CAS & HT on NLB.

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RE: Exchange 2010 HA Questions - 11.Nov.2009 12:27:15 PM   
neilho

 

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quote:

ORIGINAL: ismail.mohammed

hi mate,

I agree with Mark as well.
If I need to go with HA on Exchange 2010, two concerns will be running in my mind..
Do i need to have HA for all server roles or just i need to have HA for MBX.

If i am concerned for just MBX and few number of users then DAG where i can rest of the server roles HT, CAS.

If i am concerneed about the n numbers of mbx and HA for all server roles then i need to go with single MBX server HA and CAS & HT on NLB.


Since Outlook (MAPI) now connects to the CAS, it would seem daft to not have HA for the CAS role if you have HA for the mailbox role.

I imagine the hardware load balancer requirement for the 2 x MBX/HT/CAS server deployment in a DAG may put some people off that idea to the point where they deploy 4 servers a la CCR.

_____________________________

Neil Hobson
http://www.msexchange.org/Neil_Hobson
http://www.simple-talk.com/author/neil-hobson/

(in reply to ismail.mohammed)
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RE: Exchange 2010 HA Questions - 11.Nov.2009 12:58:48 PM   
mark@mvps.org

 

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Virtualise, virtualise, virtualise. :)
Have CASs and HTs all over the place.

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Mark Arnold (Exchange MVP)
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